YGGDRASIL - Achaea Online Help

12.1.1 YGGDRASIL

Yggdrasil, the World Tree, is a massive 'tree' of unknown origin. Whether it
is actually a tree in the sense of an oak tree, or whether the mortal mind
merely interprets it as a tree is unknown.
Regardless of what it is, it is known that it is possibly the largest living
thing in existence, spanning not only a world (its trunk supports the highest
mountains--the Pillars of Heaven--on the Achaean world and its root system
spreads through the world), but the Planes of Existence themselves. It is
said, in fact, that its roots extend through all the Infernal planes, though
this may be merely a rumour spread by those with an excess of imagination.